Fireproofing wood, vegetable fibrous materials, and textile fabrics



Patented Sept. 12, 1933 I PATEN orrica marnoorme arcs woon. vacuum aaocs MATERIALS,

H. AND mm ran- Arthur P. Allen, San mm, Calif.

No 1mm. Application September es, 1031 Serial No. 505,093

11 Claims. (01. sis-+12) The invention relates mainly tothe fire proofing of wood and wood products, vegetable fibrous materials and textile fabricabut also secures protection of the wood against the attack of insects,

decay, fungi, sap stains, moulds, etc,, as well as improving the structure of the wood, by reducing its tendency to split, check, warp, and other degrading of wood incidental to the drying and sea-. soning of lumber, and also will reduce the shrinkage and swelling of dried lumber after it has been i put in use, where it is subjected to changes in weather conditions due to moisture absorption.

The use of many of the various known fire and decay proofing materials used in the treatment 15 of wood, have not proven satisfactory, due to the salts used either darkening the wood, or makin the wood more hygroscopic'and moisture absorbing, or having deliquescent qualities which keep the surface of the wood sticky and moist, or leaches readily out bf the wood, or crystallizes and exudeson or from the surface of the wood, or prevents paints and varnishes from adhering to the wood, or stains and discolors the finished wood, or makes the wood brittle or harder to work by hand and machine tools, or causes corrosion of the steel treating tanks and equipment, etc., or are destructiv to metal fastening used in the wood, or destructive to wood working tools, or due to their low solubility, sufiicient quantity cannot be used to give the most eii'ective results, or due to their low solubility except at high temperatures, when sufllcient quantity is put into solution at a high temperature and these temperatures are lowered the salts go out ofsolution and precipitate and crystallize in and on the treating equipment; piping and valves,'etc.,' which at times filling said piping and valves with solid crystallization of the' salts, requires the dismantling of the piping system and causes a great loss of time and heavy O expense to get the crystallized salts back into solution.

After experiencing the above difliculties and after years of laboratory research, I have found 5 that the combination of aboron compound with a saccharide,- combined in proportion to their molecular weights, form a boron saccharate compound and produces a stable solution taining in complete solution the boron compound. Wherever I use the words "low solubility I refer to salts that will not go into solution in water at 50 degrees F., at a greater concentration than one to five grams of saltvto 100 grams of water, or 1 to 5% of the weight of the salt to the weight of the water. By high solubility and "high concentration, I mean 10% or greater of the weight "of thesalt to the weight of the water solvent, or 1 10 or more grams of the salt to 100 grams of water.

While this invention covers the use of the different forms of boron compounds such as sodium tetraborate, sodium metaborate, sodium perborate, boric acid and other boron salts, iii combination with a saccharide, due to its availability and low cost I prefer to use sodium tetraborate in one'or more or its forms.

Sodium tetraborate exists commercially in the three following forms: p

ADhYdIOH FNaZBQOI, molecular weight 201.27, solubility 50 F. 2%.

Pentahydrate-NazBrOvfiHzO molecular weight 291.35, solubility 50 F. 3%.

DecahydrateNazB40-1,10Hz0 molecularweight 381.43, solubility 50 F. 4.5%.'

Sodium tetraborate' is a salt formed by the union of boracic acid and sodium which when crystallized from water at ordinary temperatures separates in the form of prismatic crystals having the formula Na2B4O7,10I-I2O, or the decahydrate. If crystallized in water at a temperature above 140 degrees F., it separates in the form oi. octahedrons crystals having the formula Na:B4Oa,5H-iO. The decahydrate or prismatic form is the most common one and is ordinary borax, but the decahydrate undergoes transition into the pentahydrate, when subjected to an air temperature of about 140 degrees F. anda rela-- tive humidity around 96% and continues to lose its water of crystallization until at about 400 degrees F. it becomes anhydrous.

The stability stages of the decahydrate are about as follows i V 60 degrees F. and 54% relative humidity '10 degrees F. and 58% relative humidity degrees F. and 63% relative humidity degrees F. and 67% relative humidity 100 degrees F. and 13% relative. humidity 140 degrees F. and 96% relative humidity If the is exposed to lower humidities than the above at their corresponding temperatures it will gradually lose one or more of its molecules of water until the pentahydrate is 110 Sodium tetraborate possesses high fire resisting, fungi resisting and noncorrosive qualities, and that it is destructive to the various fungi that attack green fresh cut wood and which causes the blue stain and brown rot etc., in many species of wood, and the use of sodium tetraborate is not new in the treatment of wood, but I claim the discovery of a new compound or combination having a boron base and the application of its use with other substances, for the treatment of wood, fibrous and fabric materials.

Sodium tetraborate by itself in an aqueous solution posseesses two of the bad qualities as enumerated in paragraph two of this specification;

that of possessing a low solubility in water at atmospheric temperature which makes it diflicult to handle in the concentrations necessary to give eflectiv'e results, and that of crystallizing on the surface and in the wood, after the wood has been treated with it, which also materially effects the working and machining of the wood.

I have found that in order to produce a thorough fire proof wood it is necessary to use a concentration of sodium tetraborate in the decahydrate form, of from 15% to 30% of this material to the weight of the water in which it is held in solution. At a temperature of F. only about 2% of NazBrOv, and only about 3% of NazBrOrfiHzO, and only about 4.5% of M23401, 10H2O, of the weight of water, can be carried in water in complete solution at all temperatures, and in order to dissolve and to carry in complete solution 30% of any of these forms of sodium tetraborate, it is necessary to raise the temperature of the water containing these salts to 180 to 200 degrees F. and to maintain these temperatures at all times in the treating tanks, storage tanks, piping valves, etc., containing this solution,

causing the use and loss of a large amount of heat and its attendant cost and the use of costly heating equipment.

If for any cause the supply of heat is cut off and the temperature falls below the sustaining temperatures, precipitation and crystallizationbegins and continues as the temperature falls, when if it reaches 50 degrees F. only about 8% of the sodium tetraborate of the pentahydrate, will be held in solution and the remaining 92% will have been deposited in the form of crystals, mostly on the bottom of the container or tank holding this solution, which in the case of commercial size treating plants, having storage tanks 25 feet in diameter and 16 feet high filled with this solution, would mean the depositing of a solid mass of 50 to tons of crystallized saltsin the bottom of these tanks and making it impossible to put this salt into solution again, except at a very heavy expense and'great loss of time.

In case when wood is being treated by this solution either inan open tank or in a closed retort and where it is subjected to temperatures around 200 to 220 degrees, it is often desirable to cool the solution-down to 14.0 to 160 degrees, before discharging the solution back into the storage tanks, so as to secure greater absorption of the solution into the wood. This would cause crystallization of the sodium tetraborate and the accumulation of these crystals on the sides and bottom of the tanks or retorts and the filling up of the pipes and valves with a solid crystallization,

which would not permit the discharge of the [solution from the tanks or retorts and would necessitate the dismantling of the piping system in order to remove the salts.

substances in their anhydrous form, produces a sodium borate saccharate and permits me to carry the sodium tetraborate in complete solution at any concentration, up to the limiting solubility of the saccharide used and which forms a stable solution at all temperatures after it has been put into solution, without precipitation or crystallization. If the amount of the saccharide used is below its gram molecular proportion with that of the sodium tetraborate, complete dispersion does not occur when the solution is cooled and crystallization occurs.

The principal saccharides that are available for this purpose, at a cost that make them commercially usable are as follows:--

Dextrose, a monosaccharide, CsH12Oa, H20, molecular weight 198.11, solubility in water 80% 50 degrees F.

Commercial product, corn sugar containing about 98% dextrose.

Corn molasses, containing about 57.4 dextrose, 21.6% dextrine, 19.5% moisture, 2.5% ash. Sucrose, a disaccharide, C12H22O11, molecular weight 342.18, solubility in water about 190% 50 degrees F.

Commercial products, cane and beet sugar which are almost pure sucrose.

Cane molasses, containing about, sucrose 30%, invert sugar 30%, organic nonsugars 12%, salts 8%, moisture 20%.

Beet molasses, containing about, sucrose 50%, organic nonsugars 20%, salts 10%, moisture As I have found that the amount of a saccharide required to combine with sodium tetraborate to maintain a stable solution isin proportion to its molecular weight, that saccharide having the lowest molecular weight will require the least quantity and costs'being equal, will produce the lowest cost solution,- in which case, dextrose or a monosaccharide is the most desirable saccharide to use in my solutions.

The formula for sodium tetraborate in the form of a decahydrate or borax, is Na2B4O7 10H2O, and neglecting its water of crystallization, has a molecular weight of 201.

The formula for dextrose is Cal-1120s, H20, and neglecting its water of crystallization has a molecular weight of 180.

Then combining these two substances in their anhydrous form. in proportion to their gram molecular weights, gives 0.895 parts of Cal-1120s to 1.00 part of N312B40'LO1' expressed in percentages is equal to:-

equals 52.75%

equals 47.25%

stances are required in order to allow for their water weight to obtain the correct gram molecular proportions.

By gram molecular, one-part of sodium tetraborate, decahydrate', represented by molecularweight of 381, contains .5275 parts of sodium tetraborate anhydrous, represented by molecular weight of 201 or g g-:- equals .5275

Also by gram molecular, one part of dextrose monohydrate, represented by molecular weight 198, contains .909 parts of dextrose anhydrous, represented by molecular weight 180, or

%:g equals .909.

Then the proportions of commercial sodium tetraborate (decahydrate) and commercial dextrose' (monohydrate) that will combine completely and produce a stable solution at all temperatures without crystallization or precipitation are as follows:

Sodium tetraborate equals 1.00 part or one part .by weight of sodium tetraborate (decahydratel requires .5198 parts by weight of dextrose (monohydrate) These are the critical proportions based on chemically pure water and materials, but as these cannot be used commercially, allowances must be made so that a slight increase Dextrose equals .5198 parts of the dextrose used amounting to from .05"

to'.15 or a total of .55 to .65 parts 0! dextrose to 1.00 part of sodium tetraborate.

Then in making up my aqueous solution containing these substancesJ add to the water these two substances in proportion as above given and in proportion to the weight of the water, to secure difierent concentrations of the sodium tetraborate as followszg Quantity of dextrose required in pounds to combine with sodium tetraborate at the concentration given to maintain solubility eras; ggg 'g With Na1B401, 101110 w M N ro- N is i 2 4 1 a: a 1, critical smo critamount ical amount Critical Operating amount amount 30 29. 52 20. 4 15. 59 2] 26 24. 6 17 12. 16 20 19. 68 l3. 6 10. 39 13 l5 i4. 76 10. 2 7. 79 9. 75 10 9.84 as 5.19- 0.5

In the case where sucrose is used in the form of cane or beet sugar the quantity required is about double that of when dextrose is used due to its high molecular weightwhich 18342.18, and going through the same method or, calculations as above given with dextrose, the critical amount of sucrose required to maintain solution stability is 0.9 parts of sucrose to 1.00 part of sodium tetraborate decahydrate with the use of distilled water a I chemically pure materials, so that when commercial materials are-used an increase in the amount of sucrose is required.

In case where other forms of saccharides areused such as cane molasses, beet molasses and corn molasses, etc, no proportions can be, established for these materials from their chemical formula or molecular weights due. to their com plex and varying contents, varying moisture con tent, and their inorganic and organic nonsugar' content, and the proper proportions can only be to be used.

While in the actual commercial treatment of wood or fibrous or fabric materialsI mostly confine myself to the use of dextrose in its commercial forms such as corn sugar and corn molasses, due to the small quantity required and which produces the lowestcost solutions, this invention does not limit me to their use exclusively,

but covers the use of any of the forms of sac- 3 charides in so far as the principles of this invention are involved.

In order to put these two substances into solution it is necessary to heat the water containing these two substances up to a. temperature of about 180 degrees F. with means of agitation to expedite the dispersing until complete solution is obtained, after which the solution is ready for use and can be cooled to any temperature without precipitation or crystallization.

The actionof the boron compound not only prevents the flaming of the wood or other materials treated by it, but also prevents the attack of sap stains and moulds in the wood, and the moulding and decomposition of the solution containingthe saccharide, which without the boron compound would ferment and decompose. This boron compound also sets up a high osmotic action with the live cells of the wood and assists in diiiusingthe solution through the wood. This 1 action is well known in medicine wherein the use "of boricacid passes readily through the skin and all the live cells of the body. The boron compound. also acts as a solvent on the resins and albumens contained in the wood and assists in freeing the wood of these substances and thus enables a greater difiusion of the treating solution throughout the wood to secure complete im-, pregnatipn of the wood. a

To the combination of these two substances to form a sodium borate saccharate, I can add from 2% to 5% of sodium fluoride (NaF) for the purpose ofincreasing the fungi and decay re- 1 sisting properties of the wood. Sodium fluoride is of a veryv low solubility or about 4% in water,

but the combining of this salt with sodium tetraborate forms a sodium borate fluoride, either into NaBOz, 3NaF 01' NazBlo'z, 12NaF and its solubility is increased.

Also to the combination. of these two substances to form a sodium borate saccharate I ous oxide for this purpose is well known, but due to its low solubility the use of it has been greatly hampered in securing a concentration that will give the most eiifective results. Its solubility in water at, 35 degrees F. is only about 1% and at 104 degrees about 3% and even at these conpirical formula at 3Naz0, 6B2Oa, 5AS2O3, and enables a larger percentage to be carried in solution, and making the wood more resistant to insect attacks.

I also may combine all four ofathe above substances to form an aqueous solution of sodium fluorboron arsenous saccharate for the purpose of making the wood fire, insect and decay proof.

To any of the above solutions I may add a suitable mineral or'vegetable oil to form anemulsion, or I may add a gum or resin or colloidal substance, the boron compound assisting in dissolving these substances, or I may add liquid rubber or latex or "a synthetic rubber, or I may add a dye or coloring matter, for the purpose of moisture proofing the wood, or hardening the wood, or cementing the wood fibres together, or of improving the dielectric properties of the wood, or of, dyeing or coloring the wood.

My treating materials and solutions as above described are not only for the use of treating wood and lumber, but any fibrous vegetable materials either in their natural state or in a ground or hogged or shredded or pulp state, including wood- Waste, saw dust, bagasse, corn stalks, straw, or grasses or any other vegetable fibrous materials, or any fabric materials such as cotton, silk or wool.

The method of treating wood or lumber with any of my solutions is as follows:

Green or dried wood is placed in a'closed steel I tank or retort, and then may or may not be subjected to a steam treatment under a steam pressure of from 10 to 20 pounds per square inch, for a period of one hour more or less. It then may or may not be subjected to a vacuum of from 22 to 26 inches of mercury for a period of 15 minutes or more.

After the vacuum treatment or both steaming and vacuum treatments, the treating solution is run into the retort and the wood entirely immersed and the temperature of the solution rapidly raised to 150 or 160 degrees F. and then gradually raised to the maximum operating temperature which may be from 180 to 250 degrees F. After the operating temperature that it is desired to treat the wood has been reached, compressed air is admitted into the retort and the pressure gradually raised from atmospheric pressure to the operating pressure that itis desired to treat the wood which will range from pounds .to 250 pounds per square inch. The solution with its contained wood is then maintained under the operating temperature and pressure best suitable for the species of wood, size of wood, and the amount of absorption required, for a period of time necessary toobtain the required results.

The time required under the maximum operating temperature and pressure will vary from one to six hours for one inch thick lumber and for a longer time for thicker lumber.

The solution is then gradually cooled down to a temperature of about .150 degrees by means of pipe coils within the retort through which cold water is circulated. This cooling period may last from one to three hours for one inch thick lu mber after which the solution is removed from the retort and discharged into storage tanks to be used over again and the lumber is removed from the retort and either dried in the air or in a dry kiln.

During the latter part of the operating temperature and pressure period, the temperature number of times in order to increase the penetration of the solution into the lumber.

After this treatment has been made and the wood impregnated with the borate saccharate solution, I may remove the solution from the, retort and leaving the wood in the retort, treat the wood with a second aqueous solution containing a soluble metallic salt, for the purpose of combining with the borate salt, to form an insoluble metallic borate on and near the surface of the wood structure, so as to prevent the leaching or dissolving out of the wood the borate salts impregnated therein during the first treatment, after the wood is put into use where it is subjected to moist or wet conditions.

My method of treatment with this second solution differs from any now in practice. In former processes the wood is removed from the retort after the first treatment and then dried in a dry kiln, and then after it is dried it is placed back into the retort for the second treatment, or the wood-is subjected to a vacuum after the first treatment, in order to draw out a part of the first solution so as to permit the entrance of the second solution, or the wood is subjected in the first treatment to a lower pressure than in the second treatment combined with a vacuum, in order to 100 secure a penetration of the wood with the second solution. The removal of the wood and drying it in a dry kiln and then placing it again in the retort for the'.second treatment is very expensive, requiring a double kiln drying of the wood. Also the putting of a vacuum on'the wood after the first treatment draws out the solution from the wood with its contained salts and treating materials and thus weakens the effect of the treating materials placed in the wood by the first treatment.

With my methods I removethe first treating solution from the retort at a high temperature below the boiling point or around 200 to 210 degrees and then cool quickly the retort chamber and the atmosphere surrounding the wood, by means of cooling coils through which cold water is circulated, or by 'means of cold water sprays, or by means of cold air circulating around the wood, or a combination of these means of quickly cooling the surface of the wood, with the result that I get a partial evaporation of the waterof the solution contained in the wood, due to the inside of the wood being at a high temperature with a cold exterior, causing a flow of the moisture out of the wood in the form of a vapor or steam, leaving all the salts and treating materials contained in the solution deposited in and on the wood fibres, thus causing a partial dehydration of the wood without any loss of the salts or treating 3 materials from the wood which occurs when a vacuum is used.

treatment, but for a shorter period of time and permitting this solution tocool downto about degrees before removing the solution from the retort in order to secure increased absorption of the solution.

It is not the intention with this invention to secure complete penetration of the wood with the.

second treating solution, but only a partial 150 penetration, in order to form an insoluble metallic treatment of all sap wood or shredded or hogged borate salt at and near the surface of the wood and retaining the original qualities of the salts and treating materials contained in the first treating solution which has been impregnated throughout the wood.

Of the sulfate salts I- may use ferrous ammonium sulfate, zinc sulfate, ferrous sulfate, copper sulfate, nickel sulfate, aluminum sulfate. 1 Ofthe chloride salts I may use barium chloride, zinc chloride, or calcium chloride, or I may use lead acetate, all of which salts when combined with sodium tetraborate form an insoluble metallic borate salt. I

In the description of my treatment I have mentioned only the use of a closed tank or retort in which the solution and its immersed wood is subjected to heat and pressure, but in the case of the treatment of all sap wood or shredded or hogged or finely divided wood or any vegetable fibre or fabric materials, I can treat in an open tank under atmospheric conditions, by using temperatures up to the boiling point and secure ample penetration, or in the case of finely divided wood or vegetable materials or fabric materials, I may merely soak the dry materials in my solution which may be hot or cold, until the materials have absorbed all the solution they will hold, after which the materials are dried, leaving the treating salts remaining in the materials treated by them.

Reference is hereby made to my copending application, Serial Number 565,917, filed Sept. 29, 1931, entitled Nondestructive partial distillation of wood, whereby additional results are obtained by the use of the materials and processes described in-this application.

While I have described certain precise'steps and recited specific temperatures, pressures, processes and chemical agents, it is not to be construed that I am limited thereto, as the examples given are to be viewed more in an illustrative than in a limiting sense since various modifications may be made without departing from the inventionas defined in the appended claims.

What I claim is:--

1. An impregnating liquid comprising a 10% or more of a borate salt, and a smaller amount of a saccharide, in proportion to their gram molecular weight, in an aqueous solution, in order to produce and maintain solubility of the borate salt.

2. A process of treating wood, vegetable fibrous materials and textile fabrics, which comprises subjecting them to the action of an aqueous solution containing 10% or greater of a borate salt, to which is added a smaller amount of a saccharide, combined in proportion to their gram molecular weights, in order to increase the solubility of the borate salt.

3. A process of treating wood, vegetable fibrous materials and textile fabrics, which comprises subjecting them to the action of'an aqueous solution containing 10% or greater of a borate salt, to which is added a smaller amount of a monosaccharide, combined in proportion to their gram molecular weights, in order to increase the solubility of the borate salt.

4. A process of treating wood, vegetable fibrous materials and textile fabrics, which comprises sodium tetraborate, to which is added a smaller amount of a saccharide, combined in proportion to their gram molecular weights, in order to increase the solubility of the sodium tetraborate.

6. A process of treatitng wood, vegetable fibrous materials and textile fabrics, which comprises subjecting them to the action of an aqueous solution containing 10% or greater concentration of sodium tetraborate, to which is added a smaller amount of dextrose, combined in proportion to their gram molecular weights, in order to increase the solubility of the sodium tetraborate.

7. A process of treating wood, vegetable fibrous materials and textile fabrics, which comprises subjecting them to the action of an aqueous solution containing 10% or greater concentration of sodium tetraborate, to which is added a smaller amount of sucrose, combined in proportion to their gram molecular weights, inorder to increase the solubility of the sodium tetraborate.

8. A process of treating wood, vegetable fibrous materials and textile fabrics, according to claim 5 to which is added sodium fiuoride to the solution.

9. A process of treating wood, vegetable fibrous materials and textile fabrics, according to claim 5, to which is added an arsenic salt to the solution.

10. A process of treating wood, vegetable. fibrous materials and textile fabrics, according to claim 5, and then subjecting the wood or materials to the action of a second aqueous solution containing a soluble metallic sulfate salt, that will combine with the borate salt and form an insoluble'borate salt.

11. A process of treating wood, vegetable fibrous materials and textile fabrics, according to claim 5, and then subjecting the wood or materials to the action of a second aqueous solution containing a soluble metallic chloride salt, that will combine with the borate salt and form an insoluble borate salt.

' ARTHUR P. ALLEN. 

